Arylpyrrole carbonitrile compounds are highly effective insecticidal, acaricidal and nematocidal agents with a unique mode of action and a broad spectrum of activity. In particular, 2-aryl-5-(trifluoromethyl)pyrrole-3-carbonitrile compounds demonstrate effective control across a wide array of pests and can control resistant pests such as pyrethroid-, organophosphate-, cyclodiene-, organo-chlorine-, organotin-, carbamate-, and benzophenyl-urea-resistant biotypes of Helicoverpa/Heliothis spp., Spodoptera spp., Trichoplusia spp., Pseudoplusia spp. and Tetranychus spp. Because there is no apparent cross-resistance, 2-aryl-5-(trifluoromethyl)pyrrole-3-carbonitrile compounds and their derivatives have potential for use in resistance management programs. Further, said pyrroles have little effect on beneficial species making them excellent candidates for integrated pest management programs, as well. These programs are essential in today's crop production.
Therefore, methods to prepare said pyrroles and intermediates to facilitate their manufacture are of great use. Among the present methods to prepare 2-aryl-5-(trifluoromethyl)pyrrole-3-carbonitrile on a manufacturing scale are the 1,3-dipolar cycloaddition of 3-oxazolin-5-one with 2-chloroacrylonitrile (U.S. Pat. No. 5,030,735) and the cycloaddition reaction of the appropriate oxazole amine derivatives with 2-chloroacrylonitrile or 2,3-dichloropropionitrile (U.S. Pat. No. 5,446,170).
Also known is the 1,3-dipolar cycloaddition of the mesionic intermediate product of the acid catalyzed cyclization of a Reissert compound with a suitable alkyne to give an N-substituted pyrrole product as described by W. M. McEwen, et al, Journal of Organic Chemistry, 1980, 45, 1301-1308. However these mesionic intermediates undergo 1,4-cycloaddition reactions with ethylenic dieneophiles to give an aroylpyrrole derivative and, as such, are not useful as insecticidal arylpyrrole precursors.
Therefore, it is an object of this invention to provide a source of important intermediate ammonium oxazole and amino oxazolium compounds useful in the manufacture of arylpyrrole pesticidal agents.
It is another object of this invention to provide a method to prepare said intermediate compounds.
It is an advantage of this invention that said intermediates may be utilized in a manufacturing process which produces a formula I arylpyrrole precursor capable of being converted to a wide variety of highly effective insecticidal, acaricidal and nematocidal agents.
It is a feature of this invention that said process provides a regiospecific product. These and other features and objects of the invention will become more apparent from the detailed description set forth hereinbelow.